"Our existing infrastructure has too many bottlenecks, and it's just not going to cut it," Aden said.

Chemical maker DuPont Co. and oil giant BP PLC are working on a pilot plant in the United Kingdom that will produce butanol from such feedstocks as wheat, corn, barley and rye. The two companies also have teamed with British Sugar to develop a commercial-scale ethanol plant that eventually would be converted to produce butanol once the process is perfected.

DuPont Vice President John Ranieri said recently that the pilot plant should be operational by next year and the companies are working to make butanol cost competitive with grain ethanol by 2010.

"Once we are commercial with biobutanol, we intend to combine our technologies to make biobutanol from nonfood feedstocks," Ranieri said in a statement.

Aden said butanol as a fuel holds promise, but the technology is still in a low level of development.

"Despite what companies are saying, it's still a fair ways off," he said.

Butanol has nowhere near the political support of ethanol, and it still costs more to produce, but several companies are trying to develop technology that may make butanol cost competitive.

Gevo Inc., an Englewood, Colo.-based company backed by venture capitalists Richard Branson and Vinod Khosla, a co-founder of Sun Microsystems, said it's solving that problem with a form of E. coli bacteria.

Butanol producers to date have used Clostridium acetobutylicum bacteria to munch on a variety of sugary feedstocks to produce acetone, butanol and ethanol.

By substituting an E. coli derivative developed by scientists at UCLA, Gevo is able to produce only isobutanol, said Pat Gruber, the company's chief executive.

Gruber said the process is already under way at a small 20,000-gallon-per-year pilot plant in Colorado. The next step is to join with ethanol plant designer ICM Inc. to build a larger scale facility at ICM's biofuels research center in St. Joseph, Mo.

Gevo's business model is to take existing ethanol plants and retrofit them into butanol plants, a transformation Gruber estimates would cost between 25 cents and 30 cents per gallon in capital.

Aden said butanol faces several challenges if production costs can be reduced.

More scientific research is needed to develop new bacteria strains and enhance yields, and engineers will have to address some challenges. Butanol is heavily toxic to the bacteria that break it down, so companies are going to have to move beyond simple distillation methods to extract the substance.

But Aden sees butanol eventually providing another choice for the consumer who pulls up to the pump.

"A lot of it is going to hinge on the success of research over the next five years," he said.